Clinical and laboratory investigations in patients with chronic myelogenous leukemia have been facilitated by the fact that patients with this disorder have (1) abundant granulocytes for periods of time off treatment, (2) undergoes a transition from a premalignant to a highly malignant disease as part of its natural history. In the past year, efforts have been primarily directed toward using the granulocyte of this disease as a human tissue source for the study of a new granulocyte-labelling isotope, Gallium 67.